RFR: 8290464: Optimize ResourceArea zapping on ResourceMark release [v2]

[Coleen Phillimore]

On Tue, 19 Jul 2022 14:56:57 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> We have `ResourceMark` scopes where we either do not resource-allocate at all (see the bug for the example), or we do not allocate a lot in the arena. Still, in debug builds, we are zapping the entirety of `ResourceArea` chunk in those cases. This wastes testing cycles unnecessarily. Doing this in a bit smarter way -- zapping only the parts that were actually allocated in the chunk -- makes testing significantly faster.
>> 
>> Linux x86_64 fastdebug, `tier1`:
>> 
>> 
>> # Before
>> real 26m33.621s
>> user 1156m56.676s
>> sys 52m18.291s
>> 
>> # After
>> real 25m29.573s  ; -4.0%
>> user 1089m27.179s ; -5.8%
>> sys 52m17.630s
>> 
>> 
>> Additional testing:
>>  - [x] Linux x86_64 fastdebug, `FieldSetAccessibleTest` (~12% faster)
>>  - [x] Linux x86_64 release, `FieldSetAccessibleTest` (no regressions)
>>  - [x] Linux x86_64 fastdebug, `hotspot:tier1` (~6% faster)
>>  - [x] Linux x86_64 release, `hotspot:tier1` (no regressions)
>>  - [x] Linux x86_64 fastdebug, `tier1` (~4% faster)
>>  - [x] Linux x86_64 release, `tier1` (no regressions)
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review comments: simplify

yeah, keep "replaced" the comments tell you what it means.

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PR: https://git.openjdk.org/jdk/pull/9543